Seven-year thermal-vacuum real-life test of a solar array drive mechanism manufactured by Marconi Space and Defence Systems (Model No. 002)

A solar array drive mechanism underwent 1 rev/day for 7 yr in an environmental test chamber. Angular rotation stability remains well within the specified limit. Slip-ring electrical noise increased substantially during the first 2 yr. There was then a small reduction during the following 3 yr followed by a small increase towards the end of the test. Several signal slip-ring circuits exceeded the nominal specified limit of 1 mV rms per ampere current. Two of the signal slip-ring circuits in the group carrying 500 mA current gave frequent noise transients of a very high value, indicating changes 1 ohm in the interface resistance. The distribution of these transients around the slip-rang circumference was not reproducible over long periods of time, indicating that they were probably due to the presence of variable amounts of wear debris. The noise across the power ring circuits remains well below the specified limit.